This invention relates to surgical apparatus. More particularly, this invention relates to safety apparatus for surgical instruments which ligate and cut body tissue.
The tissue is ligated by two plastic clips ejected from a clip cartridge by pushers and compressed by an anvil at spaced locations about the tissue. The ligated tissue then is cut between the clips by a knife. The safety apparatus prevents operation of the instrument when there are no clips presented to the pushers which can be ejected from the instrument. The safety apparatus also includes a means to alert the surgeon that the pusher has jammed on its return stroke at the completion of a ligating and cutting operation.
Several safety devices have been proposed for surgical instruments which use metal staples or clips. U.S. Pat. No. 3,545,444 describes a suturing and cutting instrument which applies a pair of wire sutures to a tubular tissue structure inserted into an anvil assembly. The wire sutures are ejected from a cylindrical carriage assembly by a pusher. As they are ejected, the sutures are wrapped about the tubular structure by an anvil bending surface to ligate the tubular structure. When suturing is complete, the pusher advances a knife, which severs the tubular structure between the sutures. When the carriage assembly is empty, a locking spring blocks forward movement of the pusher.
U.S. Pat. No. 3,844,289 relates to a staple carrying hemostat. A surgeon clamps a bleeder by closing the jaws of the hemostat about the bleeder. The surgeon next activates a staple pusher in a staple cartridge to apply a U-shaped metal staple to the bleeder to stop the flow of blood. If the staple cartridge is empty or the staples become jammed, a spring stop blocks the staple pusher and prevents operation of the device.
U.S. Pat. No. 3,955,581 relates to a surgical instrument which ligates, sutures and divides organic tubular structures. It operates in three stages to enclose the tubular structure within the jaws of a staple cartridge, crimp the tubular structure with a pair of metal staples advanced from the cartridge by a pusher and divide the tubular structure with a knife blade advanced between the two staples. A clutch prevents retraction of the pusher and knife until the tubular structure is completely ligated, sutured and divided.
U.S. Pat. No. 4,086,926 shows a three stage device which includes a spring having a projection blocking the clip pusher when the staple cartridge is empty.
For certain surgical procedures, ligatures in the form of fasteners or clips of X-ray transparent plastic materials may be preferable to X-ray opaque metal staples. In addition to X-ray transparency, clips of plastic material also have the advantage that they can be made biologically absorbable.
Clips of plastic material cannot be substituted for metal staples in prior ligating and dividing instruments because plastic clips cannot be closed by clinching or crimping in the way that metal staples are clinched or crimped. Unlike metal staples, plastic clips will not hold a shape to which they are deformed unless parts of the clip mechanically interlock with one another. Thus, the means employed in prior ligating and dividing instruments for clinching or crimping metal staples around the tissue are not suitable for use with plastic clips.
The problems of storing and feeding plastic clips also are different from those associated with metal staples. Specifically, plastic clips must be arranged in a clip train with each clip attached to a preceding clip in the train. This allows the forwardmost clip in the clip train to be advanced by a clip pusher into position for ligating tissue structures. Because they are connected to the forward clip, the preceding clips in the clip train also are advanced. At the completion of the ligating operation, the clip pusher returns behind the next clip in the train ready for another ligating operation. The shape of plastic clips and their arrangement in a clip train require a pusher which is relatively small and delicate. The safety devices developed for prior instruments using metal staples or clips are unsuitable for a device using plastic clips because the pusher may be bent if it were blocked. Bending of the pusher would allow the knife to be advanced despite the blockage of the pusher. If the instruments were operated under these conditions, unligated tissue would be severed and injury to the patient might result.